Fluorine resins include Polyvinylfluoride resins (PVF), Polyvinylidenefluoride (PVdF), Polychlorotrifluoroethylene (PCTFE), Polytetrafluoroethylene resins (PTFE), Fluorinated ethylene-propylene copolymer resins (FEP), and Tetrafluoroethylene-perfluoroalkylvinylether copolymer resins (PFA), and it has been known that they have excellent properties. For example, they are non-tacky, have a low coefficient of friction and a good chemical resistance, and are electrical insulators. Particularly, PTFE and PFA have excellent properties.
To utilize the excellent properties of fluorine resins, attempts are being made to coat various products with the fluorine resins.
However, as the fluorine resins (particularly PTFE and PFA) have extremely high melting points (about 300.degree. C.) a coat of the fluorine resins could not be applied direct to plastics having melting points lower than those of these resins.
In products such as unit baths, particularly, FRP resins are used as raw materials, but as their melting points are as low as 120.degree.-140.degree. C., a direct PTFE resin finishing of the raw material surface can not be conducted.
In recent years, therefore, a number of fluorine resin-mixed type coating materials have been invented, and methods have been adapted to apply a coat of these materials to a material surface to be coated.
Such conventional fluorine resin coating materials have an inconvenience in that they show the characteristics of fluorine resins early in the application to a product, but they peel away when used for a long time because of their lack of adhesion to the coated material surface.
Therefore, it is an object of this invention to provide a method of coating with PTFE resins, which makes it easy to apply the resins to plastic products and gives excellent adhesion of coating materials to the products.